Improve CircleCI setup

[meddle0x53]

Motivation

As part of #2996 , we are doing a few experiments with the CircleCI startup and provisioning logic as part of this PR. The idea is to speedup the setup part of the logic and remove some issues with hanging builds.

Test Plan

Use the CI and its workflows to test that times are better compared to the other PRs at the time.

Documentation

There are problems with hanging workflows, specifically the windows one, rust compilation is slow and there are repetitions, so trying to figure out how to fix these issues and we'll document the fixes which work.

• The windows workflow now doesn't get stuck (tested with over 30 tries)
• SSCache is now used (there are logs to guarantee that and it is used after a lot of small updates)
• Runtime is consistently under 25 min; Compilation on heavy libs like the synthesizes is now 2+ min faster (sscache hits).

To make it faster I see a few ways now (no other ideas):

1. Simplify and remove bad tests.
2. More partitioning.
3. Maybe bigger compilation optimisation with keeping the target folder, but this can lead to broken builds when there are big changes, so not a good idea.

[kaimast]

That looks great! I investigated similar improvements at some point (e.g., ProvableHQ/snarkOS#3680) but we never found time to finish and merge them.

Feel free to tag me as a reviewer once it is ready.

[meddle0x53]

@kaimast adding you. But am still figuring out why the sscache is not being hit properly... But looking at your PR, very similar changes, means I am on the right path!

[vicsn]

Thank you, this looks great